Edit: I noticed that you are not playing the latest version. Latest version (January 26) features that instruction text at the bottom of the options menu, like in the picture below. I'm still adding things and fixes (check last paragraph in this post).
I wasn't able to reproduce your issue, it simply doesn't happen with me (check this video, same situation as you, I tried to force the crash).
It may be low chipRAM. Even if your Workbench says "1,800,000" of chip, it isn't always true (as memory gets corrupted due to Wb apps loaded and other stuff). I would suggested to please test the vanilla CastlevaniaAGA_January2025.lha on a higher chipRAM situation: hold both mouse buttons on boot, boot with no startup, then Work: (or equivalent name of the partition) >> cd CastlevaniaAGA >> game-crunched.exe
AGA games launched from Workbench are always at risk, even with WHDLoad. Remember that back in the day, Super Stardust AGA had a boot-disk? That's the reason! A similar crash happened a while ago on AmigaBill's stream, and after that, he always used boot with no startup method (just to make sure). And since that, it always worked without problems.
It might be other incompatibility related to hardware. I would like to know what is your hardware (specially accelerator model and the KS ROM on the Amiga).
Regarding complete version, in technical terms, the game is BETA, which means that the game is feature complete, i.e., all features and content scheduled for release are in the game, including the full CD soundtrack on CD32. However, as a BETA the game is largely untested and thus has issues that need to be fixed (like what you experienced). This is why companies will do in-house betas, limited release/private betas, and public betas as their games become more solid on the way to full release. To be precise, the A1200/A4000 version is slightly behind beta because its .MOD soundtrack is still not fully complete. Hopefully, all will be finished in time for Amiga's 40th anniversary celebrations.
Thanks for playing, live streaming it and reporting! :)